Exhaust fan controller

ABSTRACT

The invention makes the decision to turn on the exhaust fan and dry out the confined space in the event that a factory predetermined moisture level has been exceeded, thereby limiting any destruction or health risks caused by negligence on the part of users or infrequent maintenance. Periodic Maintenance schedules are often extended so far as to be ineffective in moisture control. The invention takes the option to turn off the exhaust fan out of users control but not the option to turn it on. The invention is manufactured in such a way that all electronic components, sensor and pc board mounting fit into any ordinary switch box in a building electrical system and wire directly into the already installed wiring for the manual switch which it will replace.

The invention is an electronic circuit sensing moisture in any enclosed space (especially a bathroom with shower/tub) and by the use of appropriate signal conditioning, amplification, timing and on-site power switching causing the already installed exhaust fan to be switched on for a time appropriate to dry the affected space and then be automatically switched off. (In the case of the average residential bathroom this is about 20 min.)

The practical application of the invention requires the use of minature electronic components to fit into the space provided for and replacing an ordinary and standard manual switch used to switch on a room or other chosen space, exhaust fan. This invention requires no additional wiring to the building's electrical system and is a direct replacement for the manual exhaust fan switch installed as standard practise in all toilet and/or shower facilities.

BACKGROUND OF THE INVENTION

The invention provides a solution to fungal and bacterial destruction of materials used in construction of, or being stored in moist environments. The current state of the art is both inadequate and not fuctional to provide protection that can be relied upon to properly maintain dry conditions where considerable economic loss may be entailed by both user and maintainence personnel not switching on the exhaust fan manually at all, or for such short times as to be ineffective as a means of preventing the accumulation of both fungal and bacterial outbreaks that are health threatening and destructive of the structures or stored objects themselves. This situation has long been and still is a large and growing economic and health problem which this invention addresses in a cost effective and practical way.

BRIEF SUMMARY OF THE INVENTION

The invention makes the decision to turn on the exhaust fan and dry out the confined space in the event that a factory predetermined moisture level has been exceeded, thereby limiting any destruction or health risks caused by negligance on the part of users or infrequent maintainence. Periodic Maintainence schedules are often extended so far as to be ineffective in moisture control. The invention takes the option to turn off the exhaust fan out of users control but not the option to turn it on.

The invention is manufactured in such a way that all electronic components, sensor and pc board mounting fit into any ordinary switch box in a building electical system and wire directly into the already installed wiring for the manual switch which it will replace.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Vent Fan Controller Schematic, provided as FIG. 1, the components with reference labels SENS 1, R7, R1,2 & R3, Q1 and U2 comprise the moisture sensing and post sensensing conditioning circuit. The moisture sensor itself has in this case been chosen for its cost effect manufacture and low component requirements to reliably trigger the rest of the Exhaust Fan Controller circuitry. It has been made as a half inch by half inch PC board with gold leads arranged as two interleaved four pronged forks spaced at about 1/20 an inch between the tines. (Refer to FIG. 1, SENS 1 symbol details on the schematic). This is not the only sensor configuration that we have found suitable to reliably detect moisture vapor, as we have show by experiment the more expensive sensor found in generic smoke detectors can be readily used with the appropriate changes to the sensing circuit component values, which will result in the invention working in an identical fashion, but not as inexpensive to produce.

The NPN transistor(Q1) recieves the “moisure present” signal from the sensor and shapes it appropriately to be used to drive the LM311 Comparator (U2), which when the appropriate level is reached will trigger the LS7213 Timer (U5) to drive the output triac (U4) for the appropriate time chosen, which is established by the values of R9 and C5. Nominal time: 20 min. Other values chosen for particular applications, adjustable from 1 second to hours. A signal from the Timer IC (U5) pin 12, thru resister R11 to D2 will light this LED whenever the exhaust fan is on. The LED is optional but recommended.

IC U1 is a triac driver optical coupler used to isolate the 110VAC being switched on and off by the triac to the exhaust fan motor. This optoisolation decouples the triac 110VAC switching current from the low voltage supplied IC and transistors of the circuits.

The low voltage power supply shown is standard engineering practise. In this Schematic (Fig.!) the minature transformer (T1 }, full wave bridge rectifier (D1), electrolytic capacitor (C1), and the IC 5 volt regulator (U3) supply the necessary regulated 5vdc to the entire circuit. Capacitors C2, C3, C4, and C6 are bypass capacitors necessary to short unwanted voltage transients to ground.

We have also found by experiment that the power supply can benefit from slight changes, substituting a 9vdc regulator to supply the entire circuit, with the exception of the LSI timer, which requires a 5vdc regulator, makes a much more sensetive circuit, both in the lower level of moisture vapor it will detect and the speed of its response.

The Schematic (FIG. 1) shows the single 5vdc regulator option for the entire controller, and while makes it less sensetive to the amount of moisture vapor present, taking several minutes to switch on the exhaust fan motor, in most applications this delay is insignificant, in others the dual supply (9vds and 5vdc) regulators are preferred as being more sensetive and timely.

The Light Switch circuit shown at the bottom right of Schematic (FIG. 1) is another option for sites which may operate both the exhaust fan and the lights from the same manual switch. The minature low voltage switches shown on the Schematic (SW1 and SW2) make the manual switching functions of turning on the fan motor at will, or turning the room lights on and off possible from a electrical box that formerly held only one manual electrical switch. Again, the optocoupler (U6) isolates the AC being switched at the triac (U7) from the low voltage portions of the circuits. The detailed parts list is shown on the separate sheet (FIG. 2). 

1. The invention provides an economical and practical means to detect and exhaust moisture vapor from indoor spaces. In checking 20,912 patents offered by the USPTO website none were found to address or to be aimed at detecting and exhausting moisture vapor automatically from indoor spaces, as this invention provides. There is on the market a manually adjusttable humidity sensor, requiring and/or allowing the user to determine if or when the exhaust fan motor motor will be switched on. Our invention is wholly dissimular in three major ways. First, ours is not based on sensing humitity, but the more direct moisture or condensation sensing. Second, our invention is trully automatic and does not allow users the option of turning the fan motor off, but only to turn it on. The third major difference is the adapability of the various means our circuits offer to different room and electrical installations to accomplish condensation sensing and fan control. In the detail show in FIG. 3A the vent fan controller is configured to be installed as a direct replacement of an ordinary fan motor control switch. The configuration in FIG. 3B takes advantage of the flexability allowed in new installations, as this allows the exhaust fan and the controller to be mounted on the ceiling of the subject room and permanently wired there before the room walls are installed. FIG. 4 depicts a configuration that would mount on the ceiling of larger rooms, possibly in multiples, and using only the sensor, signal conditioning circuit and a minature radio frequency transmitter, would become the monitor of moisture vapor events from the more ideal location on the ceiling. Upon triggering this unit would send a radio frequency “moisture present” signal to a wall mounted reciever, timer and triac controller which would turn on the vent fan motor or motors in the case of multiple installations. Each of these different adaptations of the basic invention are necessary in certain indoor situtations, but it should be noted that all of them could utilize either the small gold tined fork sensor of FIG. 1 or the sensor found in any generic smoke detector interchanably if each sensor is given its suitable signal conditioning circuit. 